Police were investigating. No arrests had been made as of 3:30 p.m. Saturday, and police didn't have a motive. Police sources did say, however, that a man in his 20s was being questioned at the station in connection with the death of the 9-year-old boy from Palisades Park, N.J., according to the Daily News.

"This person is probably not going to be going home tonight," the police source told the News.

Meanwhile, cops were hunting through dumpsters in the housing project, General Grant Houses, and looking in elevator shafts in an apparent search for the knife that claimed the young boy's life.

Cops told the paper the boy had been visiting his grandfather for the holiday weekend.